FIELD OF THE INVENTION
The field of this invention relates to novel homo- and copolyoxadiazoles (Co-POD's) soluble in organic solvents such as m-cresol and useful as coatings, molded objects, films and fibers.
In the prior art, the article by Y. Iwakura, et al., in The Journal of Polymer Science (A) 3 page 45 (1965) a method for the synthesis of polyoxadiazoles from hydrazine sulfate and simple diacids such as terephthalic acid is disclosed. Other prior art references include the article by R. S. Jones, et al., in The Journal of Applied Polymer Science, Vol. 25, pages 315-321 (1980), British Patent Specification No. 1,455,776; Canadian Pat. No. 882,785 and the article by S. K. Varma, et al., in The Journal of Applied Polymer Science, Volume 26, pages 571-577 (1981).
The following Japanese patents further illustrate the prior art: J79,029,509-B42; J79,034, 732-B47; J80,027,918-C34 and J50,037,778-W28.
None of the foregoing references contemplates polyoxadiazoles soluble in m-cresol and useful as coatings, molded objects and films. In the book Thermally Stable Polymers by P. E. Cassidy, Marcel Dekker, Inc., New York, 1980, p. 188, the author states that "fully aromatic polyoxadiazoles are soluble only in strong acids such as concentrated sulfuric or trifluoroacetic acid."
An object of this invention is to provide copolyoxadiazoles from 5-t-butylisophthalic acid (5-tBIA), and N,N'-1,2-ethylenebis(4-carboxyphthalimide), when co-reacted with either terephthalic acid or isophthalic acid or a mixture of terephthalic acid and isophthalic acid. Another object is to provide as a novel composition of matter poly(5'-t-butyl-1',3'-phenylene-1,3,4-oxadiazole-2,5-diyl). A further object is to provide molded objects, coatings, films and fibers from the aforementioned copolyoxadiazoles and polyoxadiazoles.
I have found that the novel Co-POD's and homopolyoxadiazoles can be prepared by reacting 5-t-butylisophthalic acid with terephthalic acid or isophthalic acid or a mixture of both, and N,N'-1,2-ethylenebis(4-carboxyphthalimide) (NEBC) with hydrazine sulfate, utilizing fuming sulfuric acid as the participating reaction medium. In case of the homopolymer only the 5-t-butylisophthalic acid is reacted with hydrazine sulfate utilizing sulfuric acid as the participating reaction medium.
The reaction is conducted at a temperature of about 25.degree. to about 250.degree. C. The Co-POD's and polyoxadiazoles have an inherent viscosity measured in sulfuric acid at 25.degree. C. at about 0.6 to 6.0 or higher.
Our polyoxadiazoles comprise three broad categories of polyoxadiazoles soluble in m-cresol. They comprise:
1. A polyoxadiazole soluble in m-cresol comprising the following repeating structure: ##STR1## wherein R is an aliphatic or aromatic radical and the ratio of B units to C units and D units is about 100:100 and the ratio of C units to D units is about 1:99 to about 99:1.
The novel Co-POD's comprise moieties of the following repeating structures: ##STR2## The Co-POD's can comprise 100 percent of A moieties and still be soluble in m-cresol, however, Co-POD's comprising 100 percent B units are not soluble in m-cresol. Therefore with B units, other units set forth below have to be copolymerized.
Suitable other units use A, ##STR3## which have to be copolymerized with B units to obtain m-cresol soluble polymers.
Suitable Co-POD's soluble in m-cresol comprise ABCD units, ABC units, ABD units, AC units, AD units, AB units, and BD units and BC units, or just A units. The mole ratio of A to B units can vary from about 1:99 to about 99:1; however, all Co-POD's of this invention should comprise at least fifty mole percent of either A units or a combination of A and B units. The ratio of C to D units can vary from about 1:99 to 99:1.
The mole ratio of B to D units can vary from about 70:30 to about 30:70. In Unit B, R can be an aliphatic or aromatic moiety. Suitably when R is an aliphatic hydrocarbon the carbon chain comprises from about 1 to about 12 carbon atoms. When R is an aromatic hydrocarbon radical the carbon atoms are in the range of about 6 to about 20. The preferred values for r are (CH.sub.2).sub.2, (CH.sub.2).sub.6, ##STR4## or mixture of the last two radicals in a ratio of about 1:99 to about 99:1 preferably in a ratio of 1:1.
The novel Co-POD's are soluble in m-cresol and are useful in fiber, film, coating and molding applications. They can also be utilized as felts.
It is important that the carboxylic acids do not sulfonate or are not degraded by oleum or fuming sulfuric acid.
the novel Co-POD's have excellent thermal properties and can be molded into useful articles, cast into films and coatings, or spun into fibers.
Fibers can be manufactured from the homo- and copolymers in the following manner: The reaction solution, after completion of the polycondensation of the hydrazine sulfate with the appropriate diacid is cooled and mixed with sulfuric acid until a solution with the required viscosity is formed. The mixture is homogenized with stirring, and the resulting solution is filtered through an acid-proof fabric and deaerated under vacuum. The resulting spinning solution is formed into fibers using about a 0 to 55 percent aqueous solution of sulfuric acid as spinning batch. Non-washed, freshly formed fibers are oriented by stretching, for example, in air, or in a bath of about 0 to about 70 percent, then washed with water to remove the sulfuric acid and dried. A useful fiber spinning method is disclosed by R. S. Jones, et al., The Journal of Applied Polymer Science, Vol. 25, 315-321 (1980).